[sdiy] Vactrol control ideas wanted

[Theo]

Just PWM those suckers !

Theo


>
>
> ----- Original Message -----
> From: "harrybissell" <harrybissell at prodigy.net>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Sunday, October 19, 2003 6:09 PM
> Subject: [sdiy] Vactrol control ideas wanted
>
>
> > Hiya all...
> >
> > I'm planning a vactrol based phaser module (yeah, I know...
> > how original :^)
> >
> > I have a couple of ideas for controling the Vactrols.. like to have
> > any feedback. Maybe you've been there, done that...
> >
> > 1)  Control all the Vactrols with a series current (possibly including
> > the
> > LEDs in an opamp feedback.
> >
> > pro: its easy
> > con: it probably does not cause the interesting part of the sweep to
> > occur
> > over a wide range
> >
> > 2) Control the Vactrols by running them all in series, with one
> > Photocell fed
> > back into the control circuit.  This is an adaptation of the National
> > Semiconductor
> > "Analog Multiplier" found in AN-20.  However, this version will not have
> > one LED
> > illuminating multiple photocells.
> >
> > pro: (subject to matching) the photocell resistance can be accurately
> > specified
> > con: its more complex
> >
> > Your thoughts ladies and gentlemen ???
> >
> > H^) harry
> >
> >
>